| Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2010 Tilera Corporation. All Rights Reserved. |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or |
| 5 | * modify it under the terms of the GNU General Public License |
| 6 | * as published by the Free Software Foundation, version 2. |
| 7 | * |
| 8 | * This program is distributed in the hope that it will be useful, but |
| 9 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
| 10 | * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or |
| 11 | * NON INFRINGEMENT. See the GNU General Public License for |
| 12 | * more details. |
| 13 | */ |
| 14 | |
| 15 | #ifndef _ASM_TILE_PERCPU_H |
| 16 | #define _ASM_TILE_PERCPU_H |
| 17 | |
| Chris Metcalf | f862eef | 2013-09-26 13:24:53 -0400 | [diff] [blame] | 18 | register unsigned long my_cpu_offset_reg asm("tp"); |
| 19 | |
| 20 | #ifdef CONFIG_PREEMPT |
| 21 | /* |
| 22 | * For full preemption, we can't just use the register variable |
| 23 | * directly, since we need barrier() to hazard against it, causing the |
| 24 | * compiler to reload anything computed from a previous "tp" value. |
| 25 | * But we also don't want to use volatile asm, since we'd like the |
| 26 | * compiler to be able to cache the value across multiple percpu reads. |
| 27 | * So we use a fake stack read as a hazard against barrier(). |
| 28 | * The 'U' constraint is like 'm' but disallows postincrement. |
| 29 | */ |
| 30 | static inline unsigned long __my_cpu_offset(void) |
| 31 | { |
| 32 | unsigned long tp; |
| 33 | register unsigned long *sp asm("sp"); |
| 34 | asm("move %0, tp" : "=r" (tp) : "U" (*sp)); |
| 35 | return tp; |
| 36 | } |
| 37 | #define __my_cpu_offset __my_cpu_offset() |
| 38 | #else |
| 39 | /* |
| 40 | * We don't need to hazard against barrier() since "tp" doesn't ever |
| 41 | * change with PREEMPT_NONE, and with PREEMPT_VOLUNTARY it only |
| 42 | * changes at function call points, at which we are already re-reading |
| 43 | * the value of "tp" due to "my_cpu_offset_reg" being a global variable. |
| 44 | */ |
| 45 | #define __my_cpu_offset my_cpu_offset_reg |
| 46 | #endif |
| 47 | |
| 48 | #define set_my_cpu_offset(tp) (my_cpu_offset_reg = (tp)) |
| Chris Metcalf | 867e359 | 2010-05-28 23:09:12 -0400 | [diff] [blame] | 49 | |
| 50 | #include <asm-generic/percpu.h> |
| 51 | |
| 52 | #endif /* _ASM_TILE_PERCPU_H */ |